The present invention relates to a radio receiver such as a portable radio telephone set for receiving a signal transmitted through a radio telephone line network, a radio receiver such as a pager called by a radio signal transmitted from a base station or a signal receiver such as a telephone set connected to a wire telephone line network.
When a portable radio telephone set receives a signal transmitted from a base station or when the portable radio telephone set receives an incoming call (i.e., this telephone set is called), a calling sound signal is generated by a calling sound generator (informing means) of this telephone set. This calling sound signal is supplied to a speaker, from which it is emanated as a calling sound. The user of this telephone set can confirm the incoming call by this calling sound.
When the pager similarly receives a radio signal transmitted from the base station or when the pager is called by an incoming call, a calling sound signal is generated from a calling sound generator (informing means) of this pager. This calling sound signal is supplied to a speaker, from which it is emanated as a calling sound.
Calling sounds generated from almost all types of radio telephone sets are generally beep sounds. Beep sounds are substantially similar although they differ from one another very slightly in tone depending on the types of telephone sets. Therefore, if there are many people with the portable telephone sets around the user, then when one of these portable telephone sets is called, the user cannot determine whether the user's portable telephone is actually called or not.
The user cannot confirm the caller until the user receives an incoming call and talks with the caller. Accordingly, when a call is coming in, the user should answer the phone and confirm the caller even though the situation in which the portable telephone set is in use is changed variously at every moment, i.e., the user cannot always talk with the caller. As a result, the user of the portable telephone set cannot answer only an incoming call from a particular caller.
When the user uses a pager, the user also cannot receive only the incoming call from the particular caller. Specifically, when the pager is called, the pager never fails to inform an incoming call by generating a calling sound. Therefore, the only way that the user can select is to allow the pager to generate a calling sound or to disable the pager to receive an incoming call by turning off the power switch of the pager.
While the portable radio telephone set and the pager for receiving a radio signal are described only, a telephone set connected to a telephone line network encounters with similar problems.